The present invention relates to a circuit arrangement and a method for testing a diversity switching system.
Diversity antenna switching systems are described, for example, in European Published Patent Application No. 0 201 977. The system is essentially a single component having antenna switches and a TEA6101 diversity processor with a TDA1596 IF demodulator, both from Philips. The diversity processor detects receiving disturbances by evaluating an IF signal supplied from the radio, subsequently using the antenna switch to switch over to another antenna, the signal quality of which, in turn, is tested, etc.
This system does not make it possible to easily activate specific antennas for testing, i.e., to connect them to the radio input terminal.
A circuit arrangement that achieves this object is described in German Published Patent Application No. 195 13 872. The following is a description of this circuit arrangement, with reference to FIG. 1. Switching between (for example) four antennas 1, 2, 3 and 4 is accomplished by providing an antenna switch 5, which is controlled by a diversity processor 6. Control signals which are generated by a demodulator 10, and which demodulator 10 derives from the IF signal provided by a receiver (radio) 8 having one or more speakers 9, are present at diversity processor 6.
A converter 51, which is controlled by a control unit, e.g., radio 8, is provided to continuously activate specific antennas. To do this, the control unit generates a digital signal that is transmitted to converter 51, for example, via the antenna cable with separating filter 52, or via the IF line used to control the diversity system. Converter 51 uses electronic switches to select one of, for example, four antennas 1, 2, 3 or 4. However, because diversity processor 6 is not deactivated during testing of the selected antenna, its switching pulses may interfere with the incoming signal.
The procedure described in German Published Patent Application No. 195 13 872 has the advantage that it is relatively easy to implement. Nevertheless, it has the disadvantage that it can test only the function of the antennas, but not the function of the diversity processor itself, and the diversity processor remains in operation while the function of an antenna is being tested.
The express reference made to the above-mentioned publications and to the product description of the above-mentioned circuits also applies to all details and technical objects not described in greater detail here.
It is an object of the present invention to provide a circuit arrangement and a method for testing a diversity switching system that may be used to test not only the function of the antennas, but also that of the diversity processor itself.
In particular, the circuit arrangement according to the present invention prevents the processor from generating, during diagnosis, switching signals that interfere with the function test.
According to the present invention, a diagnostic processor is provided, which has an output terminal connected to a control input of the diversity processor and which provides, at its output terminal, a signal that prevents the diversity processor from performing any further switching operations.
In particular, use may be made of a characteristic of conventional diversity processors, such as the Philips TEA6101 circuit. This diversity processor may, for example, interrupt switching to another antenna when a stop signal is supplied to its control input.
The diagnostic processor provided according to the present invention generates the stop signal at the exact moment when it determines that the selected antenna has been activated by the diversity processor. Diagnosis is not accomplished by using an additional control unit for the antenna switch, according to the present invention, but rather the diversity processor is suitably controlled so that it continuously activates the selected antenna independently of the antenna signal at the moment.
For clarity, it should be noted that the use of the term xe2x80x9cprocessorxe2x80x9d does not imply that this circuit needs to be a microprocessor or microcontroller. xe2x80x9cHard-wiredxe2x80x9d circuits may also be used instead of processors of this type.
The circuit arrangement according to the present invention may be used, for example, to perform diagnosis as follows:
1. A frequency at which a relatively weak signal is received is first set at the radio. This is necessary because the diversity processor switches to the antenna only within the receiving level range at which noise may be heard in the speaker.
2. The number of the antenna to be set is entered at the radio either subsequently or beforehand. The radio transmits this value to the diagnostic processor.
3. Existing receiving signal fluctuations, or fluctuations that are produced, for example, by touching the antenna, cause the diversity processor to switch to another antenna. If the diagnostic processor determines that the desired antenna is set using a comparator, for example it sets the stop signal for the diversity processor. The achievement of this state is transmitted back to the radio and displayed there.
4. Switching to another antenna is an indication that the diversity processor is in proper working order. The antenna itself may then be tested, for example, by performing an audio test.
If a more thorough test of the system is necessary, for example for final inspection during manufacturing, conventional test signals may be used to test both the diversity switching threshold and the antenna function.
The directional characteristics of the individual antennas may also be tested by disconnecting the antenna cable from the radio input and supplying the antenna output signal to a measuring receiver.
According to a further example embodiment, it is possible to use special switching actions to cause the system to switch to the next antenna during diagnosis. This may be accomplished, for example, by briefly deactivating all antennas and thereby triggering switchover by the diversity processor. This action is most easily performed directly at the antenna switch at the concentration point of the switching diodes.
It is also possible to use the demodulator level signal to evaluate the antenna receiving level more precisely. In the range relevant for diversity operation, the magnitude of this signal is largely proportional to the receiving level and may therefore be compared to a reference signal during the test.
According to a further example embodiment, a test unit produced specifically for the intended purpose may be used instead of the radio as the control unit for the diagnostic processor.
Without limiting its scope and nature, the present invention is described below, by way of example, on the basis of embodiments with reference to the drawing, to which express reference is made for the purpose of describing all details according to the present invention that are not explained in greater detail in the text.